Conventionally, a rotation detection sensor for use in e.g. detection of a vehicle speed includes a sensing element accommodated in a case formed of a resin or the like and fixed to the vehicle. The sensing element is disposed in opposition to a detected portion which is attached to a detection target such as an inner wheel of a bearing and rotatable in unison with the detection target. As the sensing element detects a magnetic flux amount which varies in association with rotation of the magnetized detected portion, the rotational speed of a vehicle axle is detected. Therefore, with such rotation detection sensor, precise positioning of the sensing element relative to the detected portion is required.
A rotation detection sensor disclosed in Patent Document 1 includes a fixed member, a holder (a detecting portion) having a sensing element (a Hall-effect IC), and a case covering the sensing element (a Hall-effect IC). In an outer face of the case, a detecting face is provided and the sensing element (a Hall-effect IC) is positioned on the back side of the detecting face through insertion of a portion of the holder into the case.